Astronomy 8-16 Notes (Autosaved) - 1.1 Basic Units...

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1.1Basic UnitsAstronomical Units (AU)= means distance from the earth to the sun= 1.5x108kmSpeed of light (c)= 3.0x105km/sLight Year (LY)= distance travelled by light in one year=9.5x1012 kmParsec (pc)= distance at which 1 AU Subtends 1/3600=3.3 LY1.2Sizes of Astronomical UnitsSolar SystemTypical Distance between two stars in a galaxy-1 LYLarge Star Clusters-100 LYLarge Galaxies- 100,000 LYCluster of Galaxies- 108LY1.3Characteristic SpeedsPlanets around the sun- 10 km/sStars around the center of a galaxy- 100 km/sFragments of an Exploding Star 10,000 km/s1.4Nature of SciencePostulate has to be true but cant be provenTheories can be debunkedAstronomy Studies things that only happen outside of the nature of earths atmosphere5.1 Long term Influences on Earths ClimateMilankovitch Hypothesis: 1920- Solar heating depends on Earth’s axis and orbit, therefore changing Earth’s ClimateEllipticity: other planets Gravtitational Pull on earth Causes earths orbit to change every 100,000 yearsInclination: other planets tugs on earth perpendicular to it’s orbital plane changing the tilt of the axisPrecession- Axis slowly traces out a cone5.2 Planetary MotionMercury Jupiter orbit the same direction
Venus and Saturn orbits are coplanarEarth and Uranus Positions are relative to earthMars and Neptune are always changing5.3 Lunar Orbit and PhasesElliptical In shapeRadius is 1.3 Lightseconds in diameterInclined 5 degrees to perfect elliptic planeSidereal period is 27.33 days (time for one orbit not equal to one phaseSynodic Period is 29.5 days (full moon to full moon)5.4 Origin of TidesMoon’s total push/pull= difference in the moons gravitational force between any two parts of the earth5.5 Lunosolar TidesSun causes a tide pull tooIt is equal to one half of the moon’s total pullTwo spring and two neap tides occur monthly due to moon’s position (sun and moon lined up pulling same direction is spring tide) ((neap tide is when the moon and sun are at conjugates pulling opposite directions))6.1 Eclipse Geometry5 degree inclination of the moon makes eclipses happen in pairs twice a year
Takes place 6 months apartUmbra total shadow ( inside tight triangle)Penumbra ( inside loose triangle)6.2 Lunar EclipsesEarths Umbra is 100 Earth diameters but 2.5 moon diameters due to distanceThis causes total and partial eclipsesThe atmosphere prevents a pitch black moon6.3 Solar EclipsesOccurs when moon passes inbetween sun and earth and covers the sunMoon’s umbra on earth is 110 pmThe moons umbral coverage on earth is 270 km acrossDiamond ring effect when moon is perfectly positioned in front of thesun and causes an aurora glowing ringTotalPartialAnnular (ring like)6.4 Scientific ModelsMathematical or geometrical expression representing realityCaptures the essential behavior of phenomena such as the solar eclipse

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Term
Fall
Professor
GreggSmith
Tags
Solar System, Earths

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